html部分 

<div id="warp">
	<ul id="menu">
		<li class="firstLevel" v-for="(firstList,index) in menuData">{{firstList.title}}		
			<ul v-if="firstList.value">
				<li class="secondLevel" v-for="(secondList,index) in firstList.value">{{secondList.title}}
					<ul class="thirdLevel">
						<li v-for="(thirdList,index) in secondList.value2">{{thirdList}}</li>
					</ul>
				</li>			
			</ul>
		</li>
	</ul>
</div>

js部分

var app = new Vue({
	el:"#warp",
	data:{
		menuData: {
	        firstList:{
		        title:'练习册1', 
		        value: [
			        {
			        	title:"物理",
			        	value2:[
			        		"暑期",
			        		"寒假",
			        		"周末"
			        	]
			        },
			        {
		        	title:"化学",
		        	value2:[
		        		"暑期",
		        		"寒假",
		        		"周末"
		        		]
		        	},
		        ],
	    	},
	    	secondList:{
	    		title:'练习册2', 
		        value: [
			        {
			        	title:"政治",
			        	value2:[
			        		"暑期",
			        		"寒假",
			        		"周末"
			        	]
			    	},
			        {
		        	title:"地理",
		        	value2:[
		        		"暑期",
		        		"寒假",
		        		"周末"
		        		]
		        	},
		        ],
	    	},
	    	thirdList:{
	    		title:'练习册3', 
		        value: [
			        {
			        	title:"语文",
			        	value2:[
			        		"暑期",
			        		"寒假",
			        		"周末"
			        	]
			    	},
			        {
			        	title:"数学",
			        	value2:[
			        		"暑期",
			        		"寒假",
			        		"周末"
			        	]
		        	},
		        	{
			        	title:"英语",
			        	value2:[
			        		"暑期",
			        		"寒假",
			        		"周末"
		        		]
		        	},
		        ],
	    	}
		},          
	},
});

css部分

body{
	max-width: 640px;
	margin: 0px auto;
	font-size: 14px;
	color: #666666;
	background-color: #ffffff;
}
ul{
	padding: 0px;
}
li{
	list-style: none;
}
#menu{
	display: flex;
	justify-content: space-between;
}
.firstLevel{
	position: relative;
	min-width: 100px;
	cursor: pointer;
}
.secondLevel{
	display: none;
	margin-left: 10px;
}
.firstLevel:hover .secondLevel{
	display: block;
}
.thirdLevel{
	display: none;
	margin-left: 15px;
	width: 40px;
}
.secondLevel:hover .thirdLevel{
	display: block;
}